The present invention relates in general to lamps, and more specifically to a metal halide lamp which maximizes UV radiation in the desired useful range for curing chemical compositions.
It has long been a goal and objective in the field for a low wattage, long life, short arc gap lamp which could be used in a wide range of applications. Changing needs of the marketplace have identified the need for a short arc gap lamp in the range of 50 watts. Such an illumination source in one application could be used to irradiate small, light valves. This source would require a miniature source size, high radiance, good spectral properties, long life and low power. This goal was achieved with the development of a 50 watt arc lamp suitable for use as a projection lamp and is more fully described in U.S. Pat. No. 5,942,850.
When lamps of this type are attempted to be used in applications where UV radiation is required they are unsuitable in that even if operating conditions are modified to favorably promote UV radiation, lamp life or stability is compromised. Lamps of this type, therefore, do not satisfactorily operate to provide for enhanced radiation in the UV range, and as currently designed, are not candidates for applications where high UV response is essential.
It is therefore an object of the present invention to overcome the problems of the prior art described above.
It is a further object of the present invention to provide a high performance UV irradiation or light source which can be used as a curing light to initiate polymeric reactions in plastic and adhesive substrates.
It is a further object of the present invention to provide a high performance lamp for use in systems which require high UV radiation.
It is yet another object of the present invention to provide a compact lamp assembly which exhibits high radiance, long life, and good UV radiation.
The present invention is directed to a high performance miniature arc lamp. The lamp has a preferred use in curing chemical compositions which react to UV radiation. The lamp is used in an assembly that utilizes a dichroic coating on a reflector to concentrate UV light to the desired target or area.
It has been discovered that a unique metal halide mixture of individual compounds selected from the group of cesium iodide, indium iodide, scandium iodide, and sodium iodide provides a fill component which insures high lamp performance, and when used with a reflector having a suitable dichroic coating, is uniquely suited to providing an effective source of UV radiation.
A suitable mixture which accomplishes the objectives of the present invention comprises scandium iodide (or other suitable lanthanide), indium iodide, and alkali halides (sodium iodide and cesium iodide) in total amounts up to about 200 xcexcg. The dichroic coating is selected to reflect UV radiation in a range from about 300 to 600 nm.
For use in the present invention it is essential that the lamp be of an acceptable miniature size, exhibit high radiance, long life and low power.